1. Field of the Invention
This invention relates to processes for the utilization of polyoxyalkylene compounds as mold release agents or lubricants in molding processes.
2. Description of the Prior Art
In the molding of natural and synthetic rubber and certain other polymers, generally an efficient mold-release agent or lubricant is required to overcome the tendency of the polymer to stick to the mold which is often of metal. Both high temperatures and high molding pressures are often encountered in such molding processes. To facilitate the removal of the molded object, lubricants of the prior art have generally included mineral waxes, vegetable waxes, fatty acids, and metallic soaps, which are applied by spray or other methods of coating to the mold surface.
Polyoxyalkylene glycols have also been used as mold-release agents or lubricants for the molding of rubber wherein a metal mold is utilized. Stabilized polyoxyalkylene compositions such as those disclosed in U.S. Pat. No. 2,786,080 have been found useful, however, the phenothiazine utilized to stabilize these compositions upon dilution with water prior to application to the mold often precipitates from solution and thus its effectiveness as an antioxidant is reduced. In addition, the toxicity of such antioxidant materials as phenothiazine is undesirable in compositions which may be personally contacted.
In U.S. Pat. No. 3,504,081, there are disclosed lubricants and parting agents useful in the molding of rubber articles consisting of a mixture of dialkylphthalate, mono-alkylphenyl ether of a lower polyethylene glycol, and a higher polyethylene glycol or their alkylphenyl mono-ethers. There is no teaching that such compositions have improved resistance to oxidation under the temperature and pressure conditions utilized in molding rubber articles.
In U.S. Pat. No. 3,146,272, antioxidants for glycol derivatives are disclosed as generally any compound that is an antioxidant for polyoxyalkylene compounds which is reactive with alkylene oxides. Representative initiating compounds for the polymerization of an alkylene oxide are disclosed as phenols, alkyl phenols, aryl phenols, phenothiazine and various derivatives thereof, aryl sulfonamides, aryl amines, and alkyl aryl amines. The disclosed antioxidants are useful in combination with polyoxyalkylene compounds to reduce weight loss which occurs upon heating at elevated temperatures.
In U.S. Pat. No. 3,253,932, there are disclosed mold-release compositions consisting essentially of a polymer of an .alpha.-olefin hydrocarbon and an inert organic diluent as external lubricants, for instance, in injection molding of plastics.
A Bisphenol A, bis(propylene glycol) ether dilaurante, is disclosed as a component of a stabilized lubricant for nylon and polyester fibers in Japanese No. 76-70,397. The use of a difunctional phenol such as resorcinol as an initiator in the preparation of polyoxypropylene surfactants is disclosed in U.S. Pat. No. 2,674,619 and U.S. Pat. No. 3,036,118; the use of aromatic compounds as initiators in the production of polyoxyalkylene polymers is disclosed in U.S. Pat. No. 2,677,700; polyoxyalkylene derivatives of phenothiazine as antioxidants, for petroleum lubricants, detergents, and fungicides are disclosed in U.S. Pat. No. 2,815,343 with related uses being disclosed in U.S. Pat. No. 3,376,224 and U.S. Pat. No. 4,072,619; and the use of terminal di-vic-epoxides in the production of linear thermoplastic polyether resins based upon bisphenols is shown in U.S. Pat. No. 3,637,590. The use of same or similar polyoxyalkylene compositions of the invention as textile fiber lubricants is disclosed in U.S. Pat. No. 4,110,227.
Compositions having improved heat resistance and reduced high temperature volatility which contain an ester of an ethoxylated arylphenol are disclosed in U.S. Pat. No. 3,578,594 and the use of aromatic substituted alkylene oxides is disclosed in the production of polyoxyalkylene compounds in U.S. Pat. No. 2,677,700.
In none of these references is the utility of the oxidation-stable mold-release compositions of the invention disclosed or suggested. Accordingly, it is an object of the invention to provide to the art oxidation-stable mold-release compositions and processes for the molding of natural and synthetic rubber and other polymers wherein said mold release agents used in said compositions are resistant to volatilization under temperature and pressure conditions utilized in molding such polymers.